The aim of this paper is to analyze to what extent different kind of immunities may bar legal proceedings instituted against PMSCs and their employees. The first part of the paper is devoted to the setting of the legal background on international law rules on immunity which may be applicable, in certain cases, to PMSCs and their employees. The second part of the paper addresses the issue of immunity of PMSCs employees from criminal jurisdiction taking into account existing case-law. The conclusion is that, in most cases, immunity of private contractors from criminal jurisdiction seems not to depend on the application of immunity rules but, for a large part, from the combination of a lack of applicable rules to exercise criminal jurisdiction and a lack of political will to proceed. As to civil proceedings, the most relevant obstacle that has prevented courts form exercising their jurisdiction over PMCSs and their employees (mainly in US case-law) is the so-called “political question doctrine”, that has been invoked in most relevant civil suits and has been accepted by some courts and rejected by some others. The author of this paper is of the opinion that such a doctrine (and similar ones) was crafted to protect the exercise of governmental functions and should be narrowly interpreted. In particular, there should be no bar on judicial review when international human rights law violations occur, since the governments themselves are bound to ensure respect for these rules and shall foster a culture of accountability for their officials and for private contractors they have decided to hire.